Micro-encapsulation techniques are increasingly being developed and are widely used in the pharmaceutical, cosmetic, textile, agro-food, agrochemical, detergent and paint industries. Many hydrophilic or hydrophobic active agents can be encapsulated, such as odourant molecules, pharmaceutical active ingredients, cosmetic agents, photochromic or photoluminescent pigments, etc.
Encapsulation is an effective method for protecting an active agent from the external environment (pH, light, oxygen, humidity, etc.) thus preventing adverse phenomena such as light and/or oxygen-induced reactions. Encapsulation also helps protect an active agent from other molecules, and thus avoid incompatibility issues. Encapsulation also limits the degradation of an active agent during product conversion or storage processes. It can also make the handling or storage of these active agents easier.
There are many known methods of encapsulation. Thus, it has been suggested to encapsulate active agents by in-situ polymerization, by solvent extraction or again, by coacervation.
For example, it has been suggested to encapsulate active agents such as pharmaceutical active ingredients or agrochemical substances using HASE type acrylic polymers.
One of the major problems related to encapsulation remains the control of the subsequent release of the encapsulated active agent. For certain applications, it is important that the release of the active agent be triggered at the desired time in order for it to perform its functions. The release of the agent must therefore be able to intervene in response to a stimulus. For other applications, it is important to delay the release of the active agent (controlled release). For example, when the active agent is an odourant agent, especially an odourant agent that is chemically unstable or vulnerable to external stresses, it is important to ensure that it is stable in the initial formulation (lye, paint, scented formulations) but also stable after application to a surface (textile, wall, skin). An increase in remanence is therefore typically sought. The encapsulation processes proposed so far are generally inflexible in the method of triggering or controlling the release of the active agent, with the capsules formed usually releasing the active agent in response to a single stimulus. Thus, depending on the areas of application (for example, the pharmaceutical, cosmetic, textile, agro-food, agrochemical, detergent, paint industry) of the type of active agents, of the desired method of release, it is necessary to choose a suitable method of encapsulation.
Therefore, there is a need for the development of particles that can release an active agent in response to various stimuli, or that can delay its release. A need also exists for the development of a versatile method for the protection of an active agent, that is, a process that allows the protection of different types of active agents and enables their triggered release and/or their controlled release when one or the other is sought. This process will preferably be environmental friendly.